The trend towards compact, functional and highly integrated units in an affordable light-weight design does not pass by the safety technology either. Two developments from Pepperl+Fuchs demonstrate that e.g. safety light curtains no longer need to be large, bulky and also difficult to install. Rather, the safety components with their smart and almost cute design now fit very unobstrusively into the industrial landscape - indeed, they are almost invisible. By the way, even the evaluation unit is already included in the receiver module.
To provide the necessary personal protection at machinery with hazardous movements, non-contact protection devices with safety light curtains are frequently used. A characteristic of safety light curtains is a high number of beams with a low beam distance of normally between 14 mm and 90 mm, dependent on what needs protecting. The light curtains must be arranged in such a manner that in no case is it possible to reach over, reach under or walk behind the protective area. Detailed information on the components and measures to be used in individual cases for minimizing risks can be found in the machinery directive and the current standards.
Aluminum light-weight housing replaces heavy profiles
Whereas ordinary safety light curtains are usually contained in massive housings and require the corresponding space for operation together with expensive installations, the new generation of units is characterized by its appealing and compact design and high functionality. With a cross section of only 20 mm x 30 mm the Pepperl+Fuchs safety light curtains of series SLCS and SLCT are amongst the smallest models currently available. If you further consider that the evaluation unit is already integrated into the receiver, then the safety light curtains are really amongst the most compact models of this performance category. Their cross section is only about a quarter of the size of ordinary standard light curtains. This applies in particular at very large protection field heights of up to 2.4 m. Furthermore, the solid gold (SLCS) or silver (SLCT) anodized aluminium extrusion profiles ensure that the units are very light in weight.
Installation instead of add-on
The corresponding benefits are obvious: the low space requirement and light weight result in a much reduced construction effort for installing the safety light curtains in plant and machinery. Their extreme compactness opens up wholly new opportunities to make the safety technology almost invisible, e.g. by hiding the elements behind covers and supports or integrating them directly into existing plant components, such as profiles.
The light curtains can be mounted from three sides, i.e. on every side except the optically active side. Using the snap-in principle they are arrested with ease in an angular support bracket. This allows for installation, replacement and height adjustments to be carried out rapidly. Extrusion profiles with deep grooves are no longer required. Nonetheless, an adaptation to sliding blocks on customer mounting systems is no problem. Figure 3 shows an example of a version of this holder.
Easy commissioning and operation
Besides the design, construction and cost benefits, the safety aspect itself also benefits from the compactness of the light curtains. So far there were often installation situations - e.g. bulky angular brackets or supports - which could not prevent the unnoticed entry of hands into the hazardous area through gaps behind the light curtain. The slim safety light curtains now prevent such gaps, especially when using the available options fully in new constructions.
The commissioning and operation of the light curtains is so easy as if they were ordinary light barriers. Emitter and receiver need to be positioned correctly opposite each other and connected with an M12 cordset each; no additional wiring is required. The distance between the emitter and receiver may be up to eight meters.
Enhanced protective field thru End-on-End mounting
Units with a resolution from 30 mm support a clever End-on-End mounting. Two safety light curtains with a protection field height of up to 1200 mm each can be mounted directly on end of each other. This creates a continuous protective field with two independent switch-off areas, extending beyond a comparable master/slave solution. Because both units operate functionally independent there are additional options for the optimal adaptation of the safety technology to the requirements. The safety light curtains from Pepperl+Fuchs are amongst the few models on the market which can be mounted directly next to each other without an interruption of the protective field near the joining area. For particularly difficult operating conditions there is the option to change the operating mode by modifying the signal parameters for adjacent light curtains.
Large temperature range
Another highlight is the large operating temperature range of -30...+60 °C, which the safety light curtains meet without additional measures. This qualifies them for use also in cold stores. Until now this required a protective enclosure or housing.
100 mm longitudinal grid for tailor-made solutions
The safety light curtains of series SLCS are non-contact protection devices of type 4 in accordance with IEC 61496-1. They are self-testing and have the appropriate TÜV and UL approvals. The same goes for series SLCT, which meets the requirements of type 2 of the same standard and is testable. To detect different obstacle sizes types with a resolution of 14 mm (finger protection), 30 mm (hand protection), 60 mm or 90 mm are available. The safety light curtains can be supplied in 30 mm resolution with a protective field height of 100 mm to max. 2400 mm in graduations of 100 mm. For a resolution of 14 mm this applies accordingly with the maximum protective field height being 1200 mm. The 100 mm graduation is a particularity with which the manufacturer is replacing the common grid of 150 mm. This makes it possible to realize a tailored solution for every application.
The protective field built up by light beams of modulate infrared light is evaluated by the receiver unit. The evaluation unit integrated in the receiver controls the safety-related outputs (OSSD - Output Signal Switching Device) dependent on the detected status and continuously carries out tests to guarantee the safety function. An external test via test input is also possible here.
Conclusion
The Pepperl+Fuchs safety light curtains of series SLCS and SLCT in their compact and ultra-light design provide an ideal and affordable start-up solution to implement technical protection measures at hazardous machine components. Due to their extremely slim design they can be integrated directly into machine elements making many constructions a lot easier, not only where installation space is tight. Well thought-out detailed solutions, such as an integrated evaluation unit, End-on-End mounting and extended temperature range, make it easy for machine manufacturers to achieve ideal solutions for safety technology and optical appearance. The areas of application are in numerous industries and industry areas.
